This invention relates to regulation and control of the shifting of gears in automatic transmissions to enhance comfort.
It is generally known that there are variations of torque associated with the shifting operation in automatic transmissions which cannot be completely eliminated even in transmissions with automatic load shifting arrangements. The operator of a vehicle having such a transmission experiences these torque variations during the shifting operation as more or less pronounced jerks on the part of the vehicle. The cause of the brief acceleration which produces each jerk of the vehicle is the engagement and disengagement of clutches and brakes during each shifting of gears which heretofore have been only imperfectly matchable to each other.
In U.S. Pat. No. 4,102,222, it has been proposed, in order to achieve a noncoasting automatic transmission with improved shifting comfort, that a regulation and control system be provided in which the optimum point in time for disengaging the clutch of the previous gear is determined as a function of the measured transmission output shaft torque and the engine torque. This firstly serves to protect the shift elements to be engaged and secondly minimizes the unavoidable interruption in the driven shaft torque.
A disadvantage of this regulation and control system is that, while avoiding the need for coasting, it renders only the commencement of the shifting operation more comfortable since continuous uniformity of transmission output shaft torque is not attainable with this arrangement.
To improve the shifting comfort and hence the riding quality, German Offenlegungsschrift No. 40 23 365 proposed evaluating the quality of shifting during the operation of an automatic transmission by detecting quantities dependent on torque variations so that, after one shift operation, the shift parameters for controlling the transmission and/or the shifting components might be matched so as to optimize the next shifting operation. In this way, shift quality is improved with each shift operation by a process of trial and error.
A disadvantage of this method is that such improved transmission shifting requires a more or less prolonged breaking-in process for learning the optimum shift operation for each driving situation, since only approximately similar driving situations will result in optimally smooth shifting with the aid of learned situation-related control parameters. If such a lengthy breaking-in process is to be avoided, then it must be accepted that shift operations of diverse quality will occur throughout the life of the transmission.